Biggest ozone hole over Chile puts southern cities on sunblock alert

Ultraviolet radiation warnings have been keeping 120,000 residents of Punta Arenas, the most southerly city in Chile, virtual prisoners inside their homes this week while the sun burns high overhead.

Ultraviolet radiation warnings have been keeping 120,000 residents of Punta Arenas, the most southerly city in Chile, virtual prisoners inside their homes this week while the sun burns high overhead.

A hole in the ozone layer, which shields the earth from harmful rays that can cause skin cancers and cataracts, now extends from Antarctica over the tip of South America into populated areas. Second-stage health alerts, cautioning that unprotected skin would burn after just seven minutes exposure, were also issued in Ushuaia, Argentina, on the nearby island Tierra del Fuego.

Dr Claudio Casiccia, chief of the ozone department at the University of Magallanes, confirmed that local radiation levels hit an all-time peak on Saturday. "We are slightly below that level now but still on alert," he said. Residents venturing outdoors between 11am and 3pm were urged to wear dark glasses, sunblock, long sleeves and a wide brimmed hat, although some people ignored these warnings.

Last month, Nasa scientists announced that the seasonal ozone hole over Antarctica was the deepest on record, covering an area 50 times the size of Britain, approximately 11 million square miles.

Ozone-eating chemicals, called CFCs, include chlorine compounds found in aerosol sprays, as well as refrigerants, solvents, foam-blowing agents and compounds used in firefighting halogens. Ozone depletion first became apparent in1985.

Ozone levels have been measured in Antarctica since the 1950s. This autumn, the "near total destruction" of the ozone in some layers of the stratosphere had been noted since mid-September, much earlier than in previous years, according to United Nations climatologists. The temperature over Antarctica also has an impact on the size of the annual hole, as do polar winds.

South Africa, Australia and New Zealand are watching for increased radiation due to the expanding ozone hole. By late November, the ozone layer normally begins to thicken again.